Improvements in communications continue to be needed which help in the detection of a signal of interest and in the discernment of noise and its make up. In particular, the operators of very low frequency (VLF) systems are alert for ways to improve their performance since systems of this type have been useful to convey high priority information. Any delays in recognizing information and various interferences might have dire consequences so the need is apparent for an apparatus that visually aids an operator in making a rapid analysis of incoming signals, such as VLF, and, more particularly, the detection, interference recognition and classification of minimum shift keying (MSK) signals and/or frequency shift keying (FSK) signals in incoming VLF signals.
Because a VLF receiving terminal operator with possibly little previous knowledge about a signal of interest monitors a console for, sometimes, long periods of time, errors are always a possibility. One attempt to aid in detection in the prior art relies upon the use of previously trained operators who listen to audio outputs and develop an "ear" for judging the incoming signal traffic. A main drawback of this approach is that its success is contingent solely upon the level of operator skill which usually is found to vary from one individual to the next. Furthermore, an audio monitoring of appropriately shifted signals for a period of time will tend to become tedious and fatigue is likely with its attendant compromise of performance.
Another prior art approach to improve performance is to give an operator a visual indication by employing a spectrum analyzer to "see" the frequency characteristic of the environment. Drawbacks of this approach are that considerable expensive equipment is required to produce a relatively slow response.
Thus, a continuing need exists in the state of the art for a more accurate, cost effective visual monitoring of signals of interest to aid a receiving terminal operator in the task of determining the nature and noise environment of the incoming signals and the identifying of the signals of interest.